Getting injured is a risk for any player whether he has a history or not. Yes Given had a serious injury in 2010, we don't know if the 2011 injury was the same as the first. Also, he hasn't been injured in training since so maybe it's been fixed or at least in much better shape. I think the club will put him through a serious check up before saying yes.
Have we got Blues' goalkeeping coach? If so he worked wonders with Hart and Foster and I reckon he could improve Guzan too. His shot-stopping is very good but he is suspect when the opposition (usually Blackburn as he only plays cup games) put big buggers against him. He's still young enough to improve though.